Migrate authentication_event_archived_records to gitlab_main_user

Summary

Updates the database dictionary for authentication_event_archived_records table to reflect its migration from gitlab_main to gitlab_main_user schema.

What does this MR do?

• Updates db/docs/authentication_event_archived_records.yml to specify the new schema location
• Aligns the table configuration with our sharding guidelines
• Updates the sharding issue

Why are we making this change?

The gitlab_main schema is being deprecated as part of our database sharding initiative. All tables currently residing in gitlab_main need to be migrated to their appropriate target schemas.

Schema Migration Details

• Table: authentication_event_archived_records
• From: gitlab_main
• To: gitlab_main_user
• Feature Category: system_access

Review Request

@jknabl-gitlab

Related Links

• Database Sharding Guidelines
• [Schema Migration Tracking Issue] (#556057)
• [Schema Selection Guidelines] (https://docs.gitlab.com/development/cells/#available-cells--organization-schemas)